Packing of cohesive angular particles: Cohesive strength, structure, and effects of angularity

Employing extensive 2D contact dynamics simulations, we analyze the effects of grain shape angularity on the quasistatic shear strength properties of cohesive granular packings. We consider sticky irregular polygons ranging from disklike shapes to triangle. We find that the Mohr-Coulomb cohesion (i.e., the cohesive strength) is an increasing function of grain angularity. Meanwhile, the macroscopic friction angle increases with angularity and saturates for the most angular shapes, similar to dry cases. Using an effective stresslike approach, we show that the Mohr-Coulomb cohesion emerges from the cohesive force network for all shapes. From this, a micromechanical model reminiscent of the so-called "Rumpf" formula, is derived and reveals the increasing competition between the macroscopic friction, the anisotropy of the cohesive contacts network, and the grain shape parameter (i.e., the number of sides of the polygons) in the variation of Mohr-Coulomb cohesion with increasing angularity.